Inherently tacky pressure sensitive adhesive (PSA) acrylic polymers formed by emulsion polymerization are well known in the art as replacements for solution adhesive polymers.
The water borne pressure-sensitive adhesives utilize acrylic monomers to provide low glass transition temperatures (Tg) to the inherently tacky copolymer, unsaturated carboxylic acid monomers to enhance adhesion to polar surfaces and multifunctional monomers to improve cohesive strength with minimal loss of loop tack and other properties.
Vinyl esters, such as vinyl acetate are incorporated to enhance cohesive strength and peel adhesion and reduce cost but create problems in production. Typical residual vinyl ester monomer content has been high, ranging from about 0.5 to about 1 percent by weight of total monomers fed to the emulsion polymerization reactor. It is ecologically desirable to reduce residual monomer content in emulsion polymerization and to provide enhanced adhesive properties. This is the subject of the instant invention.